NOUS41 KWBC DDHHMM AAE
PNSWSH
Technical Implementation Notice 11-53, Amended
National Weather Service Headquarters Washington DC
330 PM EDT Mon Apr 16 2012
To: Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
-NOAAPORT
-Other NWS Partners, Users and Employees
From: Tim McClung
Chief, Science Plans Branch
Office of Science and Technology
Subject: Amended: Changing the Rapid Update Cycle (RUC) to the
Rapid Refresh (RAP) Analysis and Forecast System:
Effective date set for May 1, 2012.
Amended to set the implementation date for Tuesday May 1, 2012.
Users are cautioned that if a Critical Weather Day (CWD)
designation is in effect on May 1, this implementation will be
delayed until the conclusion of CWD. You can monitor the CWD
status at the following webpage:
http://www.nco.ncep.noaa.gov/pmb/cwd/
Also amended to add a clarification about shelter specific
humidity replacing shelter mixing ratio in the bgrb files.
On Tuesday, May 1, 2012, beginning with the 1200 Coordinated
Universal Time (UTC) run, the National Centers for Environmental
Prediction (NCEP) will replace the Rapid Update Cycle (RUC) with
the Rapid Refresh (RAP) model. Changes include:
-Covering a much larger domain, compared to the RUC,
including Alaska and the Caribbean basin and almost all of
North America
-Introducing a new modeling framework
-Installing a major upgrade to the prediction model
-Modifying the data analysis and assimilation system
-Matching most existing RUC products and adding new ones to
cover the expanded domain. A select number of obsolete RUC
files will be removed.
-Introducing experimental North American Rapid Refresh Ensemble
using Time Lagged (NARRE-TL) forecast.
-Modifying some product output and changing the names of all
directories and output filenames from *ruc* or *ruc2a*
to *rap*.
Details on the various changes are provided below, along with a
notice about possible changes to product generation time. NWS has
tried to capture all of the changes occurring with this
implementation. In the event that something was overlooked, we
will amend this TIN.
General Framework
Like the RUC, the RAP will be run 24 times per day, once for each
hour. Each run will be integrated to 18 hours, and output will be
available for each forecast hour. Due to the larger domain,
lateral boundary conditions for the RAP will be provided by the
Global Forecast System (GFS) instead of the North American
Mesoscale (NAM) model as is done for the RUC.
The model will be fully cycled with all fields, including snow
cover, carried through to the next cycle. The model will continue
to trim snow cover twice per day based on the NESDIS analysis. To
prevent the model from drifting away from the synoptic truth, two
6-hour partial cycles will be initiated each day at 03z and 15z
by bringing in a guess for atmospheric fields only from the GFS
and then performing a series of analyses and 1-hour forecasts
with the final 1-hour forecast used as the first guess for the 09
and 21z cycles.
Like the RUC, the RAP has a 13 km horizontal resolution and
50 vertical levels. A sigma vertical coordinate is used in the
RAP, compared to the sigma-isentropic hybrid vertical coordinate
in the RUC. The pressure top of the RAP is at 10 hPa, compared to
40-70 hPa pressure top on the highest isentropic surface in the
RUC. The native horizontal grid for the RAP is a rotated
latitude-longitude grid.
Analysis Upgrade
The Gridpoint Statistical Interpolation (GSI) analysis system has
been adapted for the RAP. It maintains several important
components of the RUC analysis:
-Cloud hydrometeor analysis
-Assimilation of radar reflectivity data
-Diabatic digital filter initialization
Additional observations are assimilated in the RAP that are not
currently assimilated in the RUC, including:
-Satellite radiances, including AMSU-A and AMSU-B, similar to
that done for the North American Mesoscale (NAM) model
-Aircraft moisture observations from UPS and Southwest
Airlines
-915-MHz profiler wind observations
-GOES cloud pressure/temperature from NASA Langley over full RAP
domain added to NESDIS cloud data already assimilated in RUC
Model Upgrade
The RAP model component is a configuration of the Weather
Research and Forecasting (WRF) model, using the Advanced Research
WRF (ARW) core. It keeps, however, mostly RUC-like physics
including:
-A version of the Grell convective scheme
-Thompson cloud and precipitation microphysics
-Rapid Radiation Transfer Model (RRTM) longwave radiation
-Goddard shortwave radiation
-MYJ (Mellor-Yamada-Janjic) planetary boundary layer (PBL)/
turbulent mixing
-RUC/Smirnova land-surface model.
Updated versions of the cloud microphysics, Grell convection,
and RUC land-surface schemes are used in the RAP over older
versions used in the RUC.
Output Product Changes
The RUC currently generates output on pressure levels (pgrb) and
native levels (bgrb) at horizontal resolutions of 13, 20 and 40
km for every forecast hour (0-18). Smaller files with near-
surface data (sgrb) are generated at a smaller number of forecast
hours at the same resolutions, and an 80 km data set generated
for a few forecast hours is also available. The RUC output is
made available to users on the NWS ftp server, the NCEP server,
and a subset of the output is available on NOAAPORT.
The NWS issued a Public Information Statement(PNS) on November 9,
2011 requesting comments on the proposal to remove several RUC
products. Please see:
http://www.nws.noaa.gov/os/notification/tin11-36ruc.htm
Based on the responses received, the decision was made to
terminate the following RUC products as part of this
implementation:
-All sgrb data.
-80 km data.
-Native level output at 40 km resolution.
Please see the PNS referred to above for specifics about the
exact files to be removed and the dissemination outlets for these
files.
The following new data sets will be available on the NCEP server,
with output at all forecast hours:
-Full domain 32-km grid (AWIPS grid 221).
-11 km Alaska grid (AWIPS grid 242).
-16 km Puerto Rico grid (AWIPS grid 200).
To facilitate a smooth transition from the RUC to the Rapid
Refresh, NCEP is making look-alike files in the RAP to mimic
output provided by the RUC. Files with data on native levels
(bgrb) and pressure levels (pgrb) will be provided on the same
130 (13 km) and 252 (20 km) grids currently generated by the RUC.
In addition, RAP pgrb data (not bgrb) will be provided on the 236
(40 km) grid. NCEP has tried to match the fields offered by the
RUC, but there are a few exceptions listed below resulting from
the use of the NCEP unified post processor. When a RUC parameter
is unavailable, NCEP has tried to find a similar parameter that
RAP can generate but a few fields could not be matched and were
eliminated. There are also situations in which the same parameter
is available in the RAP as in the RUC, but the Product Definition
Section (PDS) of the GRIB encoding identifies the parameter in a
different way. All of these differences are documented below.
Note that changes to the order of the parameters in the files are
not documented. It is standard NCEP practice to change the
sequence of fields in a file without documentation. Users are
advised to extract records from the files by using the PDS
instead of using the order of records.
Also note that these look-alike files, which match the domain
covered by the RUC, only cover a portion of the expanded RAP
domain: 32-km full-domain files on grid 221 will be available in
the RAP. No full-domain data sets will be available at any other
resolution other than 32 km: 11-km files on grid 242 will be
available for users wanting high-resolution RAP output over
Alaska , and 16-km files on grid 200 will be available for users
wanting high-resolution RAP output over Puerto Rico .
The differences between RAP and RUC files are discussed below:
BGRB (native levels):
-The vertical profile of virtual potential temperature
(parameter 189) in the RUC is replaced by temperature
(parameter 11) in the RAP.
-The vertical profile of mixing ratio (parameter 53, vertical
coordinate 109) in the RUC is replaced by specific humidity
(parameter 51) in the RAP. The shelter value (vertical
coordinate 105) of mixing ratio in the RUC is also replaced by
specific humidity in the RAP.
-The net longwave flux at the surface (parameter 112) in the RUC
is replaced by the surface downward longwave flux (parameter
205) in the RAP.
-The net shortwave flux at the surface (parameter 111) in the
RUC is replaced by the surface downward shortwave flux
(parameter 204) in the RAP.
-The RAP maintains 3-hr buckets for convective and non-
convective precipitation like the RUC, but it adds in 1-hr and
run total buckets.
-The lightning parameter (187) now has values in the RAP where
1 indicates a model prediction of an ongoing thunderstorm, and
0 is the null event. The RUC field currently contains zeros at
all points.
-The rate of water dripping from canopy to ground (parameter
188) is not available in the RAP.
-The fields of snow temperature (parameter 239) at 5 and 10 cm
are not available in the RAP.
-The field of surface mixing ratio (parameter 53) and density
(parameter 89) at 5 cm are eliminated.
-The storm-surface and baseflow-groundwater runoff parameters
are now 1-hr accumulations in the RAP, compared to the
instantaneous values in the RUC.
-The following new parameters are added to the bgrb files: PBL
height (parameter 221), surface height (parameter 7 at
surface), surface wind gust (parameter 180), skin temperature
(parameter 11 at surface), friction velocity (parameter 253),
and upward longwave flux at the top of the atmosphere
(parameter 212 at TOA).
-The "best" convective available potential energy (parameter
157) and convective inhibition (parameter 156) fields are now
true values of those parameters rather than being calculated
using moist static energy as in the RUC. These fields in the
RAP are computed using the virtual temperature correction.
-The field of shelter mixing ratio (parameter 53 at 2 meters) is
replaced by shelter specific humidity (parameter 51 at 2
meters).
PGRB (PRESSURE LEVELS):
-The surface-based lifted index (parameter 131) now has the
vertical coordinate defined as 101 (layer being two isobaric
levels) with 500 and 1000 as the two levels. The RUC defines it
as a surface field (vertical coordinate 1). This parameter is
now computed using the virtual temperature correction.
-The "best" lifted index (parameter 132, labeled as computed
between 0 and 180 mb) replaces the best lifted index
(parameter 77, labeled as computed at the surface) in the RUC.
This parameter is now computed using the virtual temperature
correction.
-The 0-3 km storm-relative helicity field (parameter 190) is
correctly labeled with vertical coordinate 106 with 3000 and
0 m as the levels in the RAP; it is a surface field in the
RUC. Note that the 0-1 km helicity is correctly labeled in
both the RAP and RUC.
-The storm motion components (parameters 196 and 197) are
correctly labeled with vertical coordinate 106 with 6000
and 0 m as the levels in the RAP; they are surface fields in
the RUC.
-The storm-surface and baseflow-groundwater runoff parameters
are now 1-hr accumulations in the RAP, compared to the
instantaneous values in the RUC.
-The convective available potential energy (parameter 157) and
convective inhibition (parameter 156) fields (surface-based and
best) are now true values of those parameters rather than being
calculated using moist static energy as in the RUC. These
fields in the RAP are computed using the virtual temperature
correction.
-Cloud base height (with vertical coordinate 2) and cloud top
height (with vertical coordinate 3) now use parameter
7 (geopotential height) in the RAP; the RUC defines them as
parameter 8 (geometric distance). Also note that grid points
with no defined cloud base or top use a bitmap for this field
in the RAP; the RUC uses -9999 for the value.
-The pressure level from which a parcel used in CAPE/CIN
computations is lifted (parameter 141, vertical coordinate 116)
in the RAP replaces the pressure level of maximum equivalent
potential temperature (parameter 1, vertical coordinate 246) in
the RUC. Both parameters are computed similarly.
-The convective cloud top height field (parameter 7, vertical
coordinate 243) uses -500 as a value of no cloud in the RAP;
the RUC uses 0.
-The relative humidity computed with respect to the precipitable
water (parameter 230) now has a range of 0 to 100 in the RAP.
This parameter was incorrectly scaled by 1/100 in the RUC.
BUFR (station time-series data)
-The RAP will continue to generate station time-series BUFR data
in the formats of one monolithic file containing data for all
stations and individual station files. The RAP, however,
generates data for more stations than the RUC due to its larger
domain. The RUC currently generates data for 1168 locations; The
RAP will generate this data for 1448 locations. There will be no
change in the format or content of the data for each station.
Experimental NARRE-TL product
The new experimental NARRE-TL products are constructed from a
weighted blend of the 6 most current RAP and 4 North American
Mesoscale (NAM) forecasts covering the 01-12 hr period. The
weighting is inversely proportional to forecast length and new
01-12 hr NARRE-TL guidance is produced every hour. The parameters
are geared towards aviation needs. For CONUS:
http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE/web_site/ht
ml/conv.html
for Alaska
http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE_Alaska/web_
site/html/conv.html
In addition to these sites, this guidance will be available from
the NCEP server site.
File Names:
The file names for RAP output will differ from the equivalent RUC
files. For servers that maintain the nomenclature of the files
as they are generated, the following conversions apply:
For forecast cycle XX (00-23) and forecast hour HH (00-18):
-ruc2.tXXz.pgrb13fHH.grib2 becomes
rap.tXXz.awp130pgrbfHH (13 km)
-ruc2.tXXz.pgrb20fHH.grib2 becomes
rap.tXXz.awp252pgrbfHH (20 km)
-ruc2.tXXz.pgrbfHH.grib2 becomes
rap.tXXz.awp236pgrbfHH (40 km)
-ruc2.tXXz.bgrb13fHH.grib2 becomes
rap.tXXz.awp130bgrbfHH (13 km)
-ruc2.tXXz.bgrb20fHH.grib2 becomes
rap.tXXz.awp252bgrbfHH (20 km)
Note that for analysis files, the RUC uses an "anl" suffix; the
RAP will use the conventional "f00" for these files. For example,
ruc2.tXXz.pgrb13anl.grib2 becomes rap.tXXz.awp130pgrbf00.grib2.
The 32 km full domain files will have the naming structure
rap.tXXz.awip32fHH.grib2.
The 11 km Alaska files will have the naming structure
rap.tXXz.awp242fHH.grib2.
The 16 km Puerto Rico files will have the naming structure
rap.tXXz.awp200fHH.grib2.
Product Dissemination
The RUC output is currently available on NOAAPORT, and with the
exception of the 80km products being removed, all look-alike RAP
products will be available on NOAAPORT with the same WMO headers
as the current RUC products.
RUC output is also available on the NWS ftp server and the NCEP
server. Along with the file name changes outlined above, all
directories on these servers will change from ruc to rap. The RAP
output will be available in the following directories:
NWS FTP server:
ftp://tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.rap_CY.hh
where hh is the model cycle from 00 to 23
NCEP server:
http://www.ftp.ncep.noaa.gov/data/nccf/com/rap/prod
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/rap/prod
Product Delivery Time Changes:
The RAP cycle will be initiated each hour at the same times that
the RUC is currently initiated: 26 minutes past the hour for all
cycles, except 00/12z which are started at 58 minutes past the
hour in order to wait for raob data to become available. A major
difference in the structure of the RAP compared to the RUC
results in a major change in the availability time of the
analysis. The RUC does a preliminary posting of an analysis that
is not possible in the WRF framework of the RAP, so the RAP
analysis files will be available 12 minutes later than the
current times from the RUC. The more complex set of steps
leading to the forecast also result in later availability times
for the early RAP forecast files, but the overall code efficiency
eliminates the lag fairly quickly. For example, the 3-hour
forecast files in the RAP will be available 5 minutes later than
those from the RUC, but the delay is eliminated by forecast hour
9, and the 18-hour RAP forecast files will be available
approximately 7 minutes sooner than those currently available
from the RUC.
For more general information about the RAP, please see:
http://rapidrefresh.noaa.gov
A consistent parallel feed of data will be available on the NCEP
server once the model is running in parallel on the NCEP Central
Computing System in December. The parallel data will be available
via the following URLs:
http://www.ftp.ncep.noaa.gov/data/nccf/com/rap/para
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/rap/para
NCEP has tried to anticipate all filename and product content
changes associated with this implementation, but if we discover
additional changes during the course of the testing, we will send
an amended version of this TIN with that information as soon as
possible.
NCEP urges all users to ensure their decoders can handle changes
in content order, changes in the scaling factor component within
the product definition section (PDS) of the GRIB files, changes
to the GRIB Bit Map Section (BMS), and volume changes. These
elements may change with future NCEP model implementations.
NCEP will make every attempt to alert users to these changes
before implementation.
For questions regarding these changes, please contact:
Geoff Manikin
NCEP/Mesoscale Modeling Branch
Camp Springs , Maryland 20746
301-763-8000 X 7221
geoffrey.manikin@noaa.gov
or
Stan Benjamin
ESRL / Global Systems Division
Boulder , Colorado 80305
303-497-6387
stan.benjamin@noaa.gov
For questions regarding the dataflow aspects of these datasets,
please contact:
Rebecca Cosgrove
NCEP/NCO Dataflow Team
Camp Springs , Maryland 20746
301-763-8000 X 7198
ncep.pmb.dataflow@noaa.gov
NWS National Technical Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
$$